Along with the base server product, Microsoft also released Hyper-V Server 2012 (here's my review) and Storage Server 2012. I expect we'll soon see Essentials, currently in release candidate status, released as well.
The launch website has had availability problems (due to the high load, I'm sure) but once the dust settles it'll be worth the visit. You may or may not be interested in the collection of key notes on the home page, but you'll certainly want to look over the Technical Tracks section as it contains videos that explain many of the new OS's over 300 features. There aren't any fast forward or rewind controls for the videos, though, so you'd better pay attention.(Update: Links to the launch site are currently being redirected to the Server home page, so keep trying.)
Senior technical director Mike Otey and I have published our thoughts about this product, and it's pretty much two thumbs way up. Windows Server 2012 has such a broad array of fundamental, cost-saving, scalable, and widely usable capabilities that I predict (as I've said before) it will be the most quickly adopted server operating system in Microsoft's history.
If you are evaluating Windows Server 2012 now or plan to soon, check out my Getting around in Windows Server 2012 Part 1 (using the Start screen in Server) and Part 2 (quick start to using Server Manager). Our Windows Server 2012 home page has a ton of information, based on almost a year's experience, to help you quickly come up to speed.
Senior technical analyst Paul Thurrott and I will also be hosting a Twitter chat on Windows Server 2012 tomorrow at 3 PM Eastern Daylight Time. We'd love to hear your opinions, and we may have a special guest or two drop by to say hello. Just create a search for #ws2012insider.
You can download an evaluation version of Windows Server 2012 from the Microsoft Windows Server home page, or from your current subscription's download center. Hyper-V Server 2012's free download is available from the Server and Cloud Platform page.
Follow Sean on Twitter at @shorinsean.